1. Field of the Invention
The present invention relates to a process and apparatus for rapidly altering, both upwards and downwards, the temperature of a liquid or thick fluid in a closed vessel. The invention also relates to a process and apparatus for maintaining the treated liquid at the raised or lowered temperature. The invention is especially suitable for use with hermetically closed glass bottles.
It is known that the suddenness in such changes in temperature is highly desirable in some activities, particularly in the areas of pharmacy and foodstuffs, for example for fruit and vegetable juices, for milk products, for beer and for cider, and in general terms for all food products which need to be protected against fermentation, the protective technique then used involving pasteurizing the product and then cooling it as quickly as possible, within a maximum period of thirty minutes, to prevent deterioration of the product which would result from its rise in temperature.
2. Prior Art
To cool suddenly any unit consisting of a glass bottle (the container) and a pasteurized fluid (the content), two techniques are used at the present time, namely immersion and sprinkling or spraying.
It is known that a glass bottle filled with a very hot liquid can be immersed abruptly in cold water without any risk of breakage, since in such a case the stresses exerted on the glass are uniform at all points of the container.
The technique of abrupt immersion of a pasteurized fluid/glass unit in cold water is therefore satisfactory as regards the results which it ensures, cooling to ordinary temperature being obtained in as short a period as possible. However, this technique is used relatively rarely because it is difficult to put into practice, particularly when the pasteurized products are delivered in their sealed glass receptacles on a chain operating continuously. In particular, the surrounding moisture causes damage to some parts of the chain and this damage, even though it be minor, makes it necessary to stop the chain, with the result that this technique is incompatible with the continuous distribution of the pasteurized products.
In spite of the absolute effectiveness of the immersion technique, the sprinkling technique is preferred to it more and more often.
In this other technique, to prevent irregular stresses from being exerted on the glass, and thus to prevent probable breakages, the spraying nozzles are distributed around, above and below the glass bottles to be cooled, so as to spray effectively everywhere and thus to maintain at all points on the glass one and the same temperature at any moment of its cooling.
Nevertheless, this sprinkling technique has a major defect: because the work is carried out under high pressure, the holes in the nozzles frequently become blocked, resulting in difficulty in ensuring uniformity of spraying.
Uniformity is all the more difficult to obtain on a continuously operating chain because many glass bottles have to be cooled progressively all along the chain, so that the number of nozzles is considerable, and in addition because each nozzle is constructed with a large number of holes, in theory for assisting uniform spraying.
When the sprinkling technique is put into effect, the losses due to breakages are therefore unfortunately frequent.